From patchwork Tue Mar 7 22:22:33 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= X-Patchwork-Id: 13164835 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7575C74A5B for ; Tue, 7 Mar 2023 22:24:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231446AbjCGWXg (ORCPT ); Tue, 7 Mar 2023 17:23:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231453AbjCGWXB (ORCPT ); Tue, 7 Mar 2023 17:23:01 -0500 Received: from todd.t-8ch.de (todd.t-8ch.de [IPv6:2a01:4f8:c010:41de::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C851A4B32; Tue, 7 Mar 2023 14:22:44 -0800 (PST) From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=weissschuh.net; s=mail; t=1678227762; bh=7B9eU1poI//tORVnXKk/Isa53ZRzzHKFs17ILGS5uAY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=O14LOF3jp44o43W/cVAfN9UTGrU7Je+MZjmS8/5gJ4yidCy575yHJhQLBk5PMdFBV alOFaqyfDBKT6HrppTAb/4QzqYt6ypX8cNQd6df+N+pGhRorDA+VAvuIy4YeoqipFz d01UbPM7K8OKyuMzMPTzzciEvgC7rsCKQCHlanIg= Date: Tue, 07 Mar 2023 22:22:33 +0000 Subject: [PATCH RFC 4/5] tools/nolibc: add support for stack protector MIME-Version: 1.0 Message-Id: <20230223-nolibc-stackprotector-v1-4-3e74d81b3f21@weissschuh.net> References: <20230223-nolibc-stackprotector-v1-0-3e74d81b3f21@weissschuh.net> In-Reply-To: <20230223-nolibc-stackprotector-v1-0-3e74d81b3f21@weissschuh.net> To: Willy Tarreau , Shuah Khan Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, =?utf-8?q?Thomas_Wei=C3=9Fschuh?= X-Mailer: b4 0.12.1 X-Developer-Signature: v=1; a=ed25519-sha256; t=1678227756; l=7186; i=linux@weissschuh.net; s=20221212; h=from:subject:message-id; bh=7B9eU1poI//tORVnXKk/Isa53ZRzzHKFs17ILGS5uAY=; b=0uWbmRx4pY+W8ydurYQGxLqGKtMnVJBCi+t7ihfRpjbO56SVmFC+cnXWLko3NNRsh+oJEUd4n aMc2socQ8bFCC9xZ/UrHsR/nm6UWEQSgS8tFlk+Fwj7dTIE+whBYu5+ X-Developer-Key: i=linux@weissschuh.net; a=ed25519; pk=KcycQgFPX2wGR5azS7RhpBqedglOZVgRPfdFSPB1LNw= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Stack protection is a feature to detect and handle stack buffer overflows at runtime. For this to work the compiler and libc have to collaborate. This patch adds the following parts to nolibc that are required by the compiler: * __stack_chk_guard: random sentinel value * __stack_chk_fail: handler for detected stack smashes In addition an initialization function is added that randomizes the sentinel value. Only support for global guards is implemented. Register guards are useful in multi-threaded context which nolibc does not provide support for. Link: https://lwn.net/Articles/584225/ Signed-off-by: Thomas Weißschuh --- tools/include/nolibc/Makefile | 4 +-- tools/include/nolibc/arch-i386.h | 8 +++++- tools/include/nolibc/arch-x86_64.h | 5 ++++ tools/include/nolibc/nolibc.h | 1 + tools/include/nolibc/stackprotector.h | 48 +++++++++++++++++++++++++++++++++ tools/testing/selftests/nolibc/Makefile | 12 +++++++++ 6 files changed, 75 insertions(+), 3 deletions(-) diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile index ec57d3932506..9839feafd38a 100644 --- a/tools/include/nolibc/Makefile +++ b/tools/include/nolibc/Makefile @@ -25,8 +25,8 @@ endif nolibc_arch := $(patsubst arm64,aarch64,$(ARCH)) arch_file := arch-$(nolibc_arch).h -all_files := ctype.h errno.h nolibc.h signal.h std.h stdint.h stdio.h stdlib.h \ - string.h sys.h time.h types.h unistd.h +all_files := ctype.h errno.h nolibc.h signal.h stackprotector.h std.h stdint.h \ + stdio.h stdlib.h string.h sys.h time.h types.h unistd.h # install all headers needed to support a bare-metal compiler all: headers diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h index e8d0cf545bf1..a8deb123edca 100644 --- a/tools/include/nolibc/arch-i386.h +++ b/tools/include/nolibc/arch-i386.h @@ -180,6 +180,9 @@ struct sys_stat_struct { char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak)); +void __stack_chk_init(void) __attribute__((weak)); + +#define __ARCH_SUPPORTS_STACK_PROTECTOR /* startup code */ /* @@ -188,9 +191,12 @@ const unsigned long *_auxv __attribute__((weak)); * 2) The deepest stack frame should be set to zero * */ -void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) +void __attribute__((weak,noreturn,optimize("omit-frame-pointer"),no_stack_protector)) _start(void) { __asm__ volatile ( +#ifdef NOLIBC_STACKPROTECTOR + "call __stack_chk_init\n" // initialize stack protector +#endif "pop %eax\n" // argc (first arg, %eax) "mov %esp, %ebx\n" // argv[] (second arg, %ebx) "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx) diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h index 17f6751208e7..f7f2a11d4c3b 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -181,6 +181,8 @@ struct sys_stat_struct { char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak)); +#define __ARCH_SUPPORTS_STACK_PROTECTOR + /* startup code */ /* * x86-64 System V ABI mandates: @@ -191,6 +193,9 @@ const unsigned long *_auxv __attribute__((weak)); void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) { __asm__ volatile ( +#ifdef NOLIBC_STACKPROTECTOR + "call __stack_chk_init\n" // initialize stack protector +#endif "pop %rdi\n" // argc (first arg, %rdi) "mov %rsp, %rsi\n" // argv[] (second arg, %rsi) "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx) diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h index b2bc48d3cfe4..04739a6293c4 100644 --- a/tools/include/nolibc/nolibc.h +++ b/tools/include/nolibc/nolibc.h @@ -104,6 +104,7 @@ #include "string.h" #include "time.h" #include "unistd.h" +#include "stackprotector.h" /* Used by programs to avoid std includes */ #define NOLIBC diff --git a/tools/include/nolibc/stackprotector.h b/tools/include/nolibc/stackprotector.h new file mode 100644 index 000000000000..ca1360b7afd8 --- /dev/null +++ b/tools/include/nolibc/stackprotector.h @@ -0,0 +1,48 @@ +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ +/* + * Stack protector support for NOLIBC + * Copyright (C) 2023 Thomas Weißschuh + */ + +#ifndef _NOLIBC_STACKPROTECTOR_H +#define _NOLIBC_STACKPROTECTOR_H + +#include "arch.h" + +#if defined(NOLIBC_STACKPROTECTOR) + +#if !defined(__ARCH_SUPPORTS_STACK_PROTECTOR) +#error "nolibc does not support stack protectors on this arch" +#endif + +#include "sys.h" +#include "stdlib.h" + +__attribute__((weak,noreturn,section(".text.nolibc_stack_chk"))) +void __stack_chk_fail(void) +{ + write(STDERR_FILENO, "!!Stack smashing detected!!\n", 28); + abort(); +} + +__attribute__((weak,noreturn,section(".text.nolibc_stack_chk"))) +void __stack_chk_fail_local(void) +{ + __stack_chk_fail(); +} + +__attribute__((weak,section(".data.nolibc_stack_chk"))) +uintptr_t __stack_chk_guard; + +__attribute__((weak,no_stack_protector,section(".text.nolibc_stack_chk"))) +void __stack_chk_init(void) +{ + // raw syscall assembly as calling a function would trigger the + // stackprotector itself + my_syscall3(__NR_getrandom, &__stack_chk_guard, sizeof(__stack_chk_guard), 0); + // a bit more randomness in case getrandom() fails + __stack_chk_guard |= (uintptr_t) &__stack_chk_guard; +} +#endif // defined(NOLIBC_STACKPROTECTOR) + +#endif // _NOLIBC_STACKPROTECTOR_H diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile index ea2b82a3cd86..749a09c9a012 100644 --- a/tools/testing/selftests/nolibc/Makefile +++ b/tools/testing/selftests/nolibc/Makefile @@ -1,6 +1,8 @@ # SPDX-License-Identifier: GPL-2.0 # Makefile for nolibc tests include ../../../scripts/Makefile.include +# We need this for the "cc-option" macro. +include ../../../build/Build.include # we're in ".../tools/testing/selftests/nolibc" ifeq ($(srctree),) @@ -74,7 +76,13 @@ else Q=@ endif +CFLAGS_STACKPROTECTOR = -DNOLIBC_STACKPROTECTOR \ + $(call cc-option,-mstack-protector-guard=global) \ + $(call cc-option,-fstack-protector-all) CFLAGS_s390 = -m64 +CFLAGS_x86 = $(CFLAGS_STACKPROTECTOR) +CFLAGS_i386 = $(CFLAGS_STACKPROTECTOR) +CFLAGS_x86_64 = $(CFLAGS_STACKPROTECTOR) CFLAGS ?= -Os -fno-ident -fno-asynchronous-unwind-tables $(CFLAGS_$(ARCH)) LDFLAGS := -s @@ -118,6 +126,10 @@ nolibc-test: nolibc-test.c sysroot/$(ARCH)/include $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \ -nostdlib -static -Isysroot/$(ARCH)/include $< -lgcc +foo: foo.c sysroot/$(ARCH)/include + $(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \ + -nostdlib -static -Isysroot/$(ARCH)/include $< -lgcc + # qemu user-land test run-user: nolibc-test $(Q)qemu-$(QEMU_ARCH) ./nolibc-test > "$(CURDIR)/run.out" || :